1. Field of the Invention
Caspases are cysteinyl aspartate-specific proteinases, many of which play a central role in apoptosis. This invention relates to the identification of a new murine caspase and its human homologue. The new molecules are most related to human/murine caspase-2 and human caspase-9 and possesses all the typical amino acid residues of the caspases involved in catalysis, including the QACRG box, and contains none, or only a very short prodomain. Northern blot analysis revealed that mRNA expression of the new caspase is predominant in skin. The invention thus relates to a new caspase homologue and its use to treat human and/or animal diseases, especially skin or skin related diseases.
2. State of the Art
Members of the caspase protein family are key mediators in the execution of apoptotic cell death. Specific inhibition of one or more caspases by CrmA, p35 or the peptide derivatives Ac-YVAD-CHO and Ac-DEVD-CHO revealed that several caspases are involved in apoptosis, mediated by stimulated Fas or 55-kDa tumor necrosis factor receptor (Los et al, 1995; Bertin et al, 1997; Nagata, 1997). Both receptors transduce the death signal through a cytoplasmic sequence motif called xe2x80x9cdeath domainxe2x80x9d (DD). After receptor trimerization this domain rapidly associates with a similar DD in the adapter molecules TRADD and/or FADD. The N-terminal end of FADD exhibits significant sequence homology to two similar regions within the prodomain of procaspase-8 and procaspase-10, referred to as death effector domains (DED), which allow heterodimerization of these caspases with FADD (Boldin et al, 1996; Muzio et al, 1996; Vincenz and Dixit, 1997). In the case of Fas, it has been demonstrated that receptor occupation results in FADD-mediated recruitment of procaspase-8 into the receptor complex. Receptor-associated procaspase-8 is then proteolytically cleaved to generate active caspase-8 (Yang et al, 1998). Once procaspase-8 becomes activated, it might initiate a proteolytic caspase activation cascade, since it is able to process, at least in vitro, all known caspases into their active subunits (Srinivasula et al, 1996). Activated caspases are believed to be the executors of cell death by aspartate-specific proteolysis of substrates, which results in the characteristic features of apoptosis, such as DNA degradation, nuclear condensation, membrane blebbing, etc. (Villa et al, 1997).
A first aspect of the current invention concerns proteins and functional fragments thereof forming new members of the caspase family. Another aspect of the invention relates to nucleic acids encoding the new members of the caspase family. The invention also pertains to the screening for compounds that inhibit the synthesis and/or biological activity of the new members of the caspase family. Another aspect of the present invention is the use of these proteins, nucleic acids and/or compounds in diagnosis and/or treatment of human and/or animal diseases, especially skin diseases and/or inappropriate wound healing. A further aspect of the invention is the use of the proteins, nucleic acids or compounds to modulate keratinization. In addition a pharmaceutical preparation to treat human and/or animal diseases, especially skin diseases, comprising proteins, nucleic acids or compounds belong to the scope of the invention.
The invention thus concerns a caspase-like polypeptide comprising SEQ. ID. NO. 2 or a polypeptide with at least 80% homology to the sequence or a functional fragment of the polypeptides. In addition, the invention relates to a human caspase-like polypeptide comprising SEQ. ID. NO. 4 or a polypeptide with at least 80% homology to the sequence or a functional fragment of the polypeptides.
The invention also pertains to an isolated nucleic acid molecule comprising a nucleotide sequence encoding a polypeptide or a functional fragment thereof as mentioned above. Part of the invention is also an isolated nucleic acid molecule comprising SEQ. ID. NC). 1 or SEQ. ID. NO. 3 or a functional fragment thereof. The nucleic acid molecule of the present invention can be incorporated in a suitable vector or vector system while the vector preferably is an expression vector, in particular further comprising a regulatory element. The regulatory element directs in particular and preferably a tissue-specific expression. The scope of the current invention also belongs a genetically engineered host cell comprising the mentioned expression vector or vector present in a suitable expression system. The peptide and/or polypeptide of the invention may be used for the preparation of a medicament for the treatment of human or animal diseases such as skin diseases The peptide and/or polypeptide are extremely useful in the screening for compounds that modulate the biological activity of the peptide and/or polypeptide. Thus, the obtained compounds can be incorporated into a pharmaceutical preparation comprising in addition for instance the peptide and/or polypeptide and/or nucleic acid molecule according to the invention and suitable pharmaceutically acceptable excipients. In yet another aspect the invention features a transgenic animal harboring a nucleic acid molecule described above. In order to clarify various terms used in the current description the meaning thereof is further elaborated hereunder without being interpreted as a limitation of the scope of the invention.